Conventionally, in order to package cardboard cartons, two flaps of the cartons are folded over into a condition in which the outer edges of these two flaps are mutually in contact or a condition in which they are mutually parallel, and these flaps are joined by sticking a single piece of adhesive tape on their joining region. Carton sealers are known that perform this task automatically. With a conventional carton sealer, the entire sticky surface of the adhesive tape is stuck onto the surface of the carton.
When a cardboard carton that has been sealed in this way is unsealed by hand, it is necessary, using one's nails for example, to start peeling off the end of the adhesive tape that has been stuck down, then to grip this part using the fingertips and pull it off. However, since the adhesion of the adhesive tape is fairly strong, such an operation is not easy.
Consequently, in fact, it is usual to perform the unsealing operation by using a cutting knife to cut the adhesive tape along the outside edge of the flaps. However, with such an unsealing operation, there is a risk of the cutting knife damaging the contents. Also, since the adhesive tape that has been cut is left behind, there is the problem that, when the cardboard is recycled, considerable time is required to peel off this adhesive tape that has been left behind.
In view of the above circumstances, it is extremely convenient if an end having non-sticky outside surfaces can be formed, so that for example the adhesive tape can be pulled off using the fingertips without using a cutting knife; further, recycling is facilitated if the entire adhesive tape can easily be completely removed, and this is very beneficial from the point of view of environmental protection.
In view of the above, previously, the means has been considered of sticking a non-adhesive sheet onto the adhesive surface at the tip of the adhesive tape; however, in this case, there are the problems that non-adhesive sheet materials must be separately prepared and furthermore this is lacking in practicality because the operation is not very reliable. A carton sealer has been developed in which a width-constricting guide member for bending back the side portions in the longitudinal direction on the adhesive tape is provided at some point along the running path of the adhesive tape, having the function of forming a non-adhesive bent-back portion by making the sticky faces adhere to each other. However, since the bent-back portions produced by this carton sealer extend along the entire length in the longitudinal direction of the adhesive tape that has been made to adhere, there is the drawback that it becomes impossible to use the entire sticky surface of the adhesive tape in the joining region, resulting in the reduced strength of the seal.